A 107-turn circular coil of radius 2.85 cm is immersed in a uniform magnetic fie

Question

A 107-turn circular coil of radius 2.85 cm is immersed in a uniform magnetic field that is perpendicular to the plane of the coil. During 0.131 s the magnetic field strength increases from 57.1 mT to 98.9 mT. Find the magnitude of the average EMF, in millivolts, that is induced in the coil during this time interval?

The component of the external magnetic field along the central axis of a 78-turn coil of radius 36.0 cm decreases from 1.90 T to 0.800 T in 2.20 s. If the resistance of the coil is 3.00 ?, what is the magnitude of the induced current in the coil?

Explanation / Answer

A=pir^2 =pi*(0.0285)^2=2.55*10^-3 m^2

E=NA(dB/dt) =107*2.55*10^-3*(98-57/0.131)*10^-3

E=85.4 mV

b)

A=pir^2 =pi*0.36^2 =0.407 m^2

E=NA(dB/dt) =78*0.407*(1.9-0.8/2.2)

E=15.88 V

I=E/R =15.88/3

I=5.29 A =5.3(approx)

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